Barthes was originally a French structuralist before he wrote “Death of the Author,” a piece encouraging critics to forgo the analysis of the author’s intention. His valid argument was that most of the time, even authors didn’t quite understand what they were trying to say, and the only true human/literature relationship that mattered was the relationship between the novel and the reader.

In his work, Elements of Semiology (1967), he advanced the concept of the "metalanguage." A metalanguage is a systematized way of talking about concepts like meaning and grammar beyond the constraints of a traditional (first-order) language; in a metalanguage, symbols replace words and phrases.
Post-structuralism is defined by its relationship to its predecessor, structuralism, an intellectual movement developed in Europe from the early to mid-20th century which argued that human culture may be understood by means of a structure.
Roland Barthes
Ferdinand de Saussure
Ferdinand de Saussure is a Swiss Linguist who studies the structure of language. He is often known as the founder of modern linguistics.

The part of the sign Saussure calls the ‘concept’ or ‘meaning’ (mental impression/association of the ‘thing’) he named, ‘signified.’ The idea of what ‘Google’ is, for example, is signified. The part he calls the ‘sound-image’ (the mental ‘linguistic sign’ given to the ‘thing’) he named the ‘signifier’ – this is the sound Google’s logo creates in our minds.

As Saussure explains, the connection between all ‘signifiers’ which are ‘sound images’ or ‘linguistic signs’ and what they are signifying – their signified object or concept
THE CAT SAT ON A MAT
Sign = Signifier & Signified
(Basic) (Idea)
Example:
The cat sat on a mat = Sentence
Typography: Word "Cat" = Signifier
Meaning: Idea of a pet = Signified
Denotation, Connotation
'Denotation' tends to be described as the definitional, 'literal', 'obvious' or 'commonsense' meaning of a sign. In the case of linguistic signs, the denotative meaning is what the dictionary attempts to provide.

Connotation and denotation are often described in terms of levels of representation or levels of meaning. Roland Barthes
believes that there are different orders of signification. The first order of signification is that of denotation: at this level there is a sign consisting of a signifier and a signified. Connotation is a second-order of signification which uses the denotative sign (signifier and signified) as its signifier and attaches to it an additional signified. In this framework connotation is a sign which derives from the signifier of a denotative sign (so denotation leads to a chain of connotations).
STRUCTURE
Josef Muller-Brockmann 1914-1996
‘The designer’s work should have the clearly intelligible, objective, functional, and aesthetic quality of mathematical thinking.’

‘Working with the grid system means submitting to laws of universal validity’